This application addresses Challenge Area (05) Comparative Effectiveness Research (CER) and High Priority Topic (05-EB-105) Comparative Effectiveness of Medical Implants. Revision total joint arthroplasty (rTJA) for the hip or knee joint is a complex, costly procedure. Approximately 83,000 are performed annually in the US (2006 estimate). The frequency of these revision procedures is only expected to increase with the large number of primary total joint arthroplasty (pTJA) procedures that are expected to be performed in the coming years (estimated at over 4 million annually by 2030). Given that rTJA procedures have worse outcomes than pTJA including higher risk of complication, higher mortality, and more frequent need for further revision surgery, there is a need to both decrease the need for these procedures, but also to optimize outcomes for these revisions. The aims of this research are to: 1) evaluate the effect of patient, and institutional factors on the need for early rTJA after pTJA;2) identify the referral patterns for rTJA following first pTJA and predictors of these patterns;and 3) identify the effect of referral patterns on complications after rTJA. These aims will be accomplished by identifying state residents in New York and California undergoing their first pTJA between January 1, 1997 and December 31, 2006. These patients will be followed until the end of the study period for rTJA on the same joint. Those who have surgery with a different surgeon and at a different hospital will be considered "referrals". Patients will be identified through existing hospital discharge databases for New York and California. The effects of patient and institutional (surgeon and hospital) factors will be evaluated. In order to address the 3 specific aims, these effects will be evaluated for time to rTJA, likelihood of referral, and complications following rTJA. This will be analyzed using various multivariable models for each of the 3 aims. A Cox Regression model will be used to analyze time to rTJA for Aim 1. Aims 2 and 3 will be evaluated using a multivariable repeated measures models including methods that account for the correlation of procedures performed by the same surgeon or within the same hospital. The model for Aim 2 will evaluate the predictors of referral. The model for Aim 3 will determine whether referral improves short-term outcomes, particularly rates of surgical complication, 90 day readmission, 90 day in-hospital mortality, and subsequent revision surgery. These will be compared between patients who are referred and those who are not, adjusting for potential other confounders. It is currently unknown which patients are most at risk of early rTJA from a population perspective in the US, particularly with regard to the combination of patient and institutional factors. It is also unknown what the referral patterns are for early rTJA. It is also unknown whether geographic variation exists with regard to rTJA. Finally, it is unknown whether patients who are referred for early rTJA have better outcomes than those who have their surgery with lower volume surgeons or centers. All of these questions will be explored in this study. Quickly identifying patients most at risk for early rTJA will assist in development of future research and hopefully clinical interventions to prevent these early failures. Referral patterns and trends for rTJA have direct implications for allocation of medical resources, particularly as it pertains to training and recruitment of fellowship trained arthroplasty surgeons. Furthermore, the effect of surgeon or hospital on outcomes after early rTJA are directly relevant to improving the quality of care and reducing costs associated with these complex and already costly procedures. This project addresses an extremely important problem in our understanding of rTJA. The knowledge gained will allow us to move forward to reduce need for revision arthroplasty and to identify ways to improve outcomes following revision surgery by reducing complications and optimizing resource allocation. The strong investigative team and premier academic environment in which this study will take place assures that a high quality research will result. This analysis of administrative data represents a step forward in the use of these data to evaluate policy related questions. While previous studies in orthopedic outcomes have focused on volume outcome relationships and complications or mortality following joint replacement, this analysis moves into new territory in examining the referral patterns for revision surgery and the implications of these patterns of referral. This represents a substantial refinement in the methodology previously used for these kinds of large database analyses and will provide a template for future analyses of this kind. Revision arthroplasty is often a complex, costly procedure with worse outcomes than primary arthroplasty. Revision procedures are thought to be more commonly performed at tertiary care centers and by higher volume surgeons, but referral patterns are actually unknown. This study proposes to identify patterns for referral for revision arthroplasty in New York and California between 1996 and 2007 and to identify risk factors for early revision (within 10 years of primary surgery) and risk factors for complication following revision surgery.